# Declare a handy global variable
$global:DBNull = [System.DBNull]::Value
# Now you can test variables for DBNull
if($global:DBNull.Equals($parameterToTest)) { ... }

# Little Demo Function
function TestRefParameters {
  # OK now declare a reference parameter as an argument
  Param( [REF] $RefParam)
  # Set it! Notice you must specify the '.Value' property
  $RefParam.Value = "Test String"
}

$myRefIWantSetInFunction = "Initial Value"
# Notice we must pass it wrapped in parenthesis () with [REF]
TestRefParameters ([REF]$myRefIWantSetInFunction)
# Write Results
Write-Host $myRefIWantSetInFunction

function ReadConfig {
    Param([string] $configPath, [string] $configFilename)

    $configpath = $runningpath + '\' + $configFilename
    if(!(test-path $configpath))
    {
        Write-Host 'Configuration File Not Found: ' + $configpath
        exit 1
    }
    $global:appSettings = @{}
    $config = [xml](get-content $configpath)
    foreach ($addNode in $config.configuration.appsettings.add) {
       # Array case
       if ($addNode.Value.Contains(‘,’)) {
          $value = $addNode.Value.Split(‘,’)
          for ($i = 0; $i -lt $value.length; $i++) {
             $value[$i] = $value[$i].Trim()
          }
        }
        # Scalar case
        else {
          $value = $addNode.Value
         }
         $global:appSettings[$addNode.Key] = $value
    }
}

<?xml version="1.0"?>
<configuration>
  <startup>
    <supportedRuntime version="v2.0.50727" safemode="true"/>
    <requiredRuntime version="v2.0.50727" safemode="true"/>
  </startup>
  <appSettings>
    <!-- Plain types have no comma -->
    <add key='Version' value='1.0' />
    <!-- Array Types are comma separated -->
    <add key='ListOfNumbers' value='One,Two,Three' />
  </appSettings>
</configuration>

# Find the path where the script is executing
$runningpath = Split-Path -Parent $MyInvocation.MyCommand.Path
# Read the configuration
ReadConfig $runningpath 'myConfig.config'
# Get the version parameter
$version = $appSettings["Version"]
# Get the second element from the array parameter, notice zero based
$two = $appSettings["ListOfNumbers"][1]

function MySqlStoredProcedure {
    Param([string] $connnectionString, [{type}] $parameter1, ...)

    # Set SP Name
    $StoredProcedureName = 'pMyProc'

    # SQL Objects
    $conn = new-Object System.Data.SqlClient.SqlConnection($connnectionString)
    $conn.Open()

    $cmd = new-Object System.Data.SqlClient.SqlCommand($StoredProcedureName, $conn)
    $cmd.CommandType = [System.Data.CommandType]'StoredProcedure'

    # # # Put Parameters Here

    #execution
    $cmd.ExecuteNonQuery()

    # Get any output parameters here

    $conn.Close()
}

# Notice these are preceded with [void] to avoid extra stuff in the output...

# Here is how the return value from an SP is expressed
[void] $cmd.Parameters.Add("@return_value", [System.Data.SqlDbType]"Int")
$cmd.Parameters["@return_value"].Direction = [System.Data.ParameterDirection]"ReturnValue"

# Here is an output parameter
[void] $cmd.Parameters.Add("@ErrorCode", [System.Data.SqlDbType]"Int")
$cmd.Parameters["@ErrorCode"].Direction = [System.Data.ParameterDirection]"Output"

# A Varchar(18)
[void] $cmd.Parameters.Add("@Para1", [System.Data.SqlDbType]"varchar", 18)
$cmd.Parameters["@Para1"].Value = $taskname

# A BigInt
[void] $cmd.Parameters.Add("@BigId", [System.Data.SqlDbType]"bigint")
$cmd.Parameters["@BigId"].Value = $documentId

# Passing DBNull as a value, notice we use the value from above
[void] $cmd.Parameters.Add("@NullableParam", [System.Data.SqlDbType]"int")
$cmd.Parameters["@NullableParam"].Value = $global:DBNull

# Script can't continue and we'll also signal the error
if(Some bad thing is true) {
	Write-Error -Category Category -CategoryActivity "What the script was doing"  -message "What went wrong"
	exit 64
}